Micro-lens sheet and projection screen

ABSTRACT

In order to provide a micro-lens sheet in which unit lenses are disposed in highly accurate pitch so as to control the light diffusing characteristics of the light emission direction not only in a horizontal direction but also over 360 degrees by using the lens function of one piece of lens sheet, a micro-lens sheet has a micro-lens array section in which unit lenses are disposed in approximate matrix in a second dimensional manner on at least one surface of a base board, and the micro-lens array section is formed on only one surface of the base board, the micro-lens array section includes the unit lens having an aspherical shape, and disposition pitch of neighboring unit lenses is 200 μm or shorter.

TECHNICAL FIELD

[0001] The present invention relates to a micro-lens sheet. The presentinvention particularly relates to a micro-lens sheet which is preferableto be used for an image displaying screen (transmission projectionscreen or a rear-projection screen) for a rear-projection televisionapparatus.

[0002] Also, the present invention relates to a projection screen usinga lens array sheet which is used for a rear-projection display(television/display) such as a liquid-crystal projectiontelevision/display.

BACKGOURND ART

[0003] Commonly, in a transmission projection screen, a Fresnel lenssheet and a lenticular sheet are assembled.

[0004] A Fresnel lens sheet emits a light (which disperses from asmall-diameter lens) which is projected from a projector to a lenticularsheet as an approximate parallel light by using a converging lens.

[0005] The lenticular sheet widens horizontally a range of the projectedlight which is incident as an approximate parallel light by the Fresnellens sheet so as to emit to a person who observes the light by using acharacterized feature of a cylindrical lens group which are disposed inhorizontal direction.

[0006] Also, in a rear-projection screen, customarily, a light diffusinglayer is formed for purposes of widening a display light in a verticaldirection, making the projected light from the projector focused, andreducing unnecessary blinking which is called a scintillation in theimage because of small diameter of the lens in the projector.

[0007] The light diffusing layer is formed in at least any one among alenticular sheet, Fresnel lens sheet, or a front board such as aprotection board. For forming the light diffusing layer, methods such asapplying methods, layering methods, and mixing methods can be employedpreferably.

[0008] Recently, in place of a projector which is according to a CRTmethod having three-tube-method, liquid-crystal projector or adisplaying device using a single-tube projector according to areflection-light-bulb method such as a digital-micromirror-device(hereinafter called DMD, Trademark is registered by Texas Instrument) ora digital-light-processing device (hereinafter called DLP device,Trademark is registered by Texas Instrument) are popular. For these newdevices, preferable rear-projection-screen has been required.

[0009] The applicant for the present invention has proposed arear-projection-screen having a lenticular sheet which is disclosed indocuments such as Japanese Unexamined Patent Application, FirstPublication, No. Hei9-120101, Japanese Unexamined Patent Application,First Publication, No. Hei8-269546, Japanese Unexamined PatentApplication, First Publication, No. Hei 10-83029. Theserear-projection-screens relate to a lenticular sheet which are provideda cylindrical lens group which are disposed in horizontal direction.Therese rear-projection-screen are required to be provided with a lightdiffusing layer having a sufficient light-diffusion in any one of thecylindrical lens group.

[0010] As explained above, in a conventional lenticular sheet, it ispossible to control perspective angle (range) of the displaying lightonly in horizontal direction by using function of the lens. The controlin vertical direction depends on a light diffusing layer.

[0011] Although effect of the control of the perspective angle by usingthe lens function is high and dynamic, effect of the control of theperspective angle by using the light diffusing layer is relatively lowand softened.

[0012] Commonly, a light diffusing layer is formed by mixing a lightdiffusing particle in a resin. It is difficult to select combinationsuch as refractive indexes between the light diffusing particle and theresin, diameter of the light diffusing particle (and its distribution),and diffusion characteristics. It is also difficult to control the lightdiffusing characteristics in only vertical direction from a structuralpoint of view. Thus, it is inevitable that the light diffusingcharacteristics in a horizontal direction receive influence.

[0013] Also, it is necessary to mix excessive light diffusing particlefor enhancing the light diffusing characteristics. Therefore, reductionin the transmitted light (decrease in displaying brightness) is caused;thus, product cost increases.

[0014] Also, attempt for enhancing the light diffusing characteristicsin horizontally and vertically by using the lens function was madeconventionally. However. in addition to a lens sheet for controlling thelight diffusing characteristics in a horizontal direction, adding a lenssheet for controlling the light diffusing characteristics in a verticaldirection may cause a difficulty in aligning both lenses for setting thescreen. Also, such factors may cause increase in the product costbecause structural member increase.

[0015] A method in which a lens sheet which can control the lightdiffusing characteristics in non-horizontal direction by using the lensfunction in a screen containing a Fresnel lens sheet and the lenticularsheet instead of a lenticular sheet is disclosed in a document such asJapanese Unexamined Patent Application, First Publication, No.2000-131506.

[0016] A proposal in the above document is a lens sheet which isprovided with a micro-lens array section in which layers of micro-lenshaving optically symmetrical convex or concave shape which are disposedin a diamond-shape. In this proposal, it is necessary that a diffusingsheet layer is disposed near emission surface. Otherwise, a sheet layerin which a diffusing member is contained in the micro-lens array sectionis necessary.

[0017] In the above new device, as represented by an XGA standard, inorder to provide a high-resolution image quality, more fine resolutionfor a panel (such as a liquid crystal or a micro-mirror array) forregulating the projected image is sought according to an increase inpixels. More fine resolution in parallel disposition pitch of thecylindrical lens group is required for a screen.

[0018] Also, along with realization in finer resolution in paralleldisposition pitch for a unit lens, finer resolution for a lighttransmitting section in a shading pattern (Black Matrix hereinaftercalled BM) which is formed away from the lens section has been realized.Therefore, accuracy for forming an aperture section in a lightcondensing section where a light is condensed by the micro-lens arraysection clearly is required.

[0019] In case of a lens sheet having a fine pitch lens section, a blackmatrix is formed by so called a self-alignment method in which positionsof non-light-condensing section for the lens are determined accuratelyby using light condensing characteristics by the lens to aphotosensitive resin layer which is formed on the lens sheet away fromthe lens.

[0020] For self alignment method, there are a wet method in which theshading pattern is formed after developing the exposed photosensitiveresin layer, or a dry method in which the shading pattern is formedapplying a color without developing the exposed photosensitive resinlayer.

[0021] In dry method, a photosensitive adhesion agent having acharacteristics in which bonding characteristics occurs according towhether or not light is exposed is used, and a color is appliedcorresponding to the adhesion.

[0022] In order to form a BM having preferable shading ratio (forobtaining preferable contrast in image, a range such as more than 60% isexperimentally preferable) for a transmission liquid crystal projectionscreen, the position of light condensation (focus) by the lens sectionis set preferably according to the shading ratio in the formed patternin the photosensitive resin layer not on the light emission of thephotosensitive resin layer.

[0023] In a case in which a lens is spherical, positions of focal pointare different between in the center of the lens and marginal area of thelens according to aberration. Therefore, in a case in which the shadingpattern is formed by the self alignment method, the position where thecharacteristics of the photosensitive resin layer changes cannot bedetermined precisely. Therefore, a borderline between the aperturesection and the shading section is hardly clear.

[0024] In particular, in a case in which the shading ratio is enhancedso as to realize an image with higher contrast, there is a problem inthat it is difficult to form a BM having a clear borderline between afine aperture section and the shading section when parallel dispositionpitch between the unit lens is very fine and each one of the unit lensis fine.

[0025] In a conventional light transmission screen which is used in arear-projection television which is sold in a market, it is common thata Fresnel lens having a concentric gaps are formed on one surface and alenticular lens in which cylindrical lenses are disposed in onedirection are provided. A case in which either one of them is used isacceptable. Also a case in which a light diffusing layer is provided onother member can be common.

[0026] In members which is contained in these transmission screens,optical disposition is arranged such that the lights which are emittedfrom the projector are in approximate parallel state by the Fresnel lensso as to obtain horizontal perspective angle by widening the emittedlight in a horizontal direction in the image by the lenticular lens andvertical perspective angle by widening the emitted light in a verticaldirection in the image by the light diffusing member.

[0027] Furthermore, a transmission screen which can obtain a brighterand clearer image quality is known by replacing the lenticular lens by amicro-lens sheet which can obtain the horizontal perspective angle andthe vertical perspective angle compatibly without using the lightdiffusing member and by discontinuing or reducing the use of the lightdiffusing member.

[0028] Also, a method in which two lenticular layers are used such thatlongitudinal directions of the cylindrical lenses are orthogonal, or amethod in which the cylindrical lenses are disposed on both surfaces ofone base member layer such that the longitudinal directions of thecylindrical lenses are orthogonal are known.

[0029] Also, a structure in which a shading layer having aperturesections is provided in a light condensing section of each of thecylindrical lens contained in the lenticular lens or in the lightcondensing section of each of the micro-lens contained in the micro-lensarray sheet so as to improve SIN ratio of the screen is known.

[0030] Also, there is a case in which a hardcoat layer or aanti-reflection layer (hereinafter called AR layer) are provided anoutermost surface according to a usage of these transmission screen.

[0031] In a transmission screen using a conventional lenticular sheet ora micro-lens sheet, a lenticular layer and a diffusion layer arecombined so as to control the perspective angle in a horizontaldirection and a vertical direction. In the micro-lens array, widerperspective angle is necessary; therefore, there are disadvantages suchas deteriorated quality in the image due to absorption of light by thediffusion layer and white scattering, and reduced screen gain caused bywide diffusion.

[0032] Also, it is possible to propose to control the perspective anglein a horizontal direction and a vertical direction by using twolenticular layer in which longitudinal direction of each cylindricallenses are orthogonal, or by disposing a plurality of cylindrical lenson both surfaces of one base member layer such that longitudinaldirections of each of the cylindrical lens are orthogonal. In suchcases, quantity of the members contained in the cylindrical lens becomesdoubled, and very fine manufacturing process for lens also becomesdoubled. Thus, there is a problem in that cost for parts andmanufacturing process become expensive.

[0033] Also, in a screen in which two lenticular lenses are disposed onone plane surface so as to be orthogonal each other, two lenticularlenses overlap each other. Therefore, if shape of one lenticular lenschanges, optical characteristics in the other lenticular lens changesaccordingly. Thus, it is not possible to control the perspective angleby independently changing the shape of one of the lenticular lenses.Therefore, there is a limit for controlling range for the perspectiveangle; thus, such a limit is not preferable from practical point ofview.

[0034] Furthermore, in order to use a micro-lens array for atransmission screen, it is necessary to produce in a worthwhile size forthe purpose such as 50 inches in diagonal plane. In such a case, a lensthug (thickness of refractive surface) having nearly half a diameter ofan element lens is necessary for obtaining wider perspective angle.However, it is difficult to compatibly realize such depth in lens thugand picture size because of the depth to be molded. Because of this,even if necessary optical performance can be realized as long as animage area is small, due to a problem in manufacturing process, it isdifficult to enlarge the image area.

DISCLOSURE OF INVENTION

[0035] The present invention was made in consideration of aboveproblems. An object of the present invention is to provide a micro-lenssheet in which it is possible to control light diffusing characteristicsnot only in a horizontal direction but also over 360 degrees by lensfunction of one piece of lens sheet. Another object of the presentinvention is to provide a micro-lens sheet in which is preferable formanufacturing a rear projection screen containing two pieces of lenssheet in combination with a Fresnel lens sheet without using a lot oflight diffusing agent. Yet another object of the present invention is toprovide a micro-lens sheet which is preferable to observe highresolution quality image such that unit lens groups are disposed in veryfine pitch.

[0036] Yet another object of the present invention is to provide amicro-lens sheet which can control an emission direction of the displaylight emitted from the lens section in a wider perspective range (scope)by disposing the unit lens groups in fine pitch such as 200 μm or finerin a micro-lens sheet which is preferable for a lens sheet to be usedfor a transmission projection screen containing two pieces of lens sheetin combination particularly with a Fresnel lens sheet.

[0037] Yet another object of the present invention is to provide amicro-lens sheet which can easily form a fine BM in which a borderlinebetween an aperture section and the shading section is clear when a BMhaving a high shading ratio (75%) is formed on a micro-lens sheet awayfrom the lens section.

[0038] Yet another object of the present invention is to provide aprojection screen using a micro-lens having sufficient opticalcharacteristics for a screen with less optical absorption, less gainreduction, and controlled white scattering easily with large area.

[0039] Yet another object of the present invention is to provide aprojection screen using a micro-lens of which material cost andmanufacturing cost are inexpensive.

[0040] A first aspect of the present invention is a micro-lens sheethaving a micro-lens array section in which unit lenses are disposed inapproximate matrix in a second dimensional manner on at least onesurface of a base board wherein the micro-lens array section is formedon only one surface of the base board, the micro-lens array sectionincludes the unit lens having an aspherical shape, and disposition pitchof neighboring unit lenses is 200 μm or shorter.

[0041] In order to dispose a unit lens group in a fine pitch, it ispreferable that the micro-lens array section is molded by aradioactive-ray-curable-resin.

[0042] In this aspect of the present invention, it is acceptable that amicro-lens sheet has a micro-lens array section in which unit lenses aredisposed in approximate matrix in a second dimensional manner on atleast one surface of a base board wherein the micro-lens array sectionis formed such that a reacted product of a radioactive-ray-curable-resinis bonded on only one surface of the base board, the micro-lens arraysection includes the unit lens having an aspherical shape, anddisposition pitch of neighboring unit lenses is 100 μm or shorter.

[0043] It is acceptable that, in a micro-lens sheet, the micro-lensarray section has only the unit lens having aspherical shape.

[0044] Any variation in disposition of the unit lens may be acceptable.A matrix disposition which is neatly disposed in grid form, a deltadisposition in which the distance between the unit lenses is uniform, ahoneycomb disposition in which shape of the unit lens is a hexagon usingthe delta disposition can be acceptable.

[0045] Also, a disposition in which an array n and an array n+1 (n is aninteger) contained in the lens array section in the matrix dispositionare in an offset disposition by half a pitch. A shape of the unit lensarea may be a rectangle or a triangle. A triangle formed by neighboringunit lens areas can be a regular triangle sometime, and it cannot be aregular triangle sometime. By using such different cases, it is possibleto change the light diffusion characteristics in a horizontal directionand a vertical direction. In order to improve contrast in a displayedimage which is supposed to be observed in a rear projection screen, itis preferable that a shading layer is formed on a position on a surfaceof the base board which is disposed away from the micro-lens arraysection where a light is not condensed by each of unit lens.

[0046] A second aspect of the present invention is a micro-lens sheethaving a micro-lens array section in which unit lenses are disposed inapproximate matrix in a second dimensional manner on at least onesurface of a base board wherein diameter for each of the unit lens andthe disposition pitch is 200 μm or shorter, light emission angle whichis emitted from each unit lens is more than ±30 degrees against a normalof a main surface of the micro-lens sheet; chromatic difference ofmagnification which is caused by each unit lens is designed to be in arange of 0% <chromatic difference of magnification ≦50% of the diameterof the lens.

[0047] A third aspect of the present invention is a projection screenhaving the micro-lens sheet having the micro-lens array section in whichthe unit lenses are disposed in an approximate matrix in asecond-dimensional manner wherein a surface of the unit lens is formedin toric shape as a continuous surface such that curvature of crosssectional shape of the unit lens in one direction is smaller than thatin an orthogonal direction to the particular direction, the micro-lensarray section in which the unit lens is disposed in an approximatematrix in a second-dimension manner is formed on one surface of thetransparent sheet, and the shading layer having the aperture section ofwhich optical axis is aligned with the optical axis of unit lens groupon a surface of the sheet which is disposed opposite to the micro-lensarray section.

[0048] In a fourth aspect of the present invention, it is characterizedin that, in a projection screen, directions of the curvature of eachunit lens are uniformly disposed when the micro-lens array section inwhich the unit lens is disposed in an approximate matrix in asecond-dimension manner is formed on one surface of the transparentsheet.

[0049] In a fifth aspect of the present invention, it is characterizedin that, in a projection screen, lens thug of the toric surface which isa ratio between thickness of a curvature section in a one direction andthickness of a curvature section in a cross sectional surface in anorthogonal direction is 2/3 or smaller.

[0050] In a sixth aspect of the present invention, it is characterizedin that, in a projection screen, lens thug of the toric surface which isa ratio between thickness of a curvature section in a horizontaldirection and thickness of a curvature section in a cross sectionalsurface in a vertical direction is 2/3 or smaller.

[0051] In a seventh aspect of the present invention, it is characterizedin that, in a projection screen, the micro-lens array section is formedon one surface of the transparent sheet which is disposed in an areafrom which a light is incident (near a projector) when the micro-lensarray section is used for a transparent projection screen.

[0052] In an eighth aspect of the present invention, it is characterizedin that, in a projection screen, the shading layer is formed in thenon-light-condensing area on a surface of a base board opposite to thelens such that a light does not condense by exposing a light through themicro-lens array section, the photosensitive resin layer or a layerwhich is formed on a surface of the photosensitive resin layer is a baseboard for a lens such that the refractive index of the layer is lowerthan that of the transparent sheet.

[0053] In a ninth aspect of the present invention, it is characterizedin that, in a projection screen further has a Fresnel lens having aconcentric ring band near a light incident region (near a projector)when the projection screen according to a first aspect of the presentinvention is used for a transparent projection screen.

BRIEF DESCRIPTION OF DRAWINGS

[0054]FIG. 1 is a cross section showing an example of a micro-lens sheetaccording to the present invention.

[0055]FIG. 2 is a plan view showing a micro-lens sheet shown in FIG. 1.

[0056]FIG. 3A is a cross section showing an optical path in a case inwhich a unit lens has a spherical shape (conventional technique). FIG.3B is a graph showing chromatic difference of magnification.

[0057]FIG. 4A is a cross section showing an optical path in a case inwhich a unit lens has an aspherical shape as defined as the presentinvention. FIG. 4B is a graph showing chromatic difference ofmagnification.

[0058]FIG. 5 is a cross section showing an example for a micro-lenssheet according to the present invention.

[0059]FIG. 6 is a curve showing an example for a cross sectional shapeof a unit lens according to the present invention in which there is lesschromatic difference of magnification.

[0060]FIG. 7 is a graph showing a distribution of exposure on a BMsurface in case in which a unit lens has an aspherical shape as definedin the present invention.

[0061]FIGS. 8A and 8B are general views for a micro-lens sheet used in aprojection screen according to the present invention.

[0062]FIG. 9 is a perspective view of an element lens contained in themicro-lens array sheet used in the projection screen according to thepresent invention.

[0063]FIG. 10 is a cross section of an element lens in a verticaldirection contained in the micro-lens array sheet used in the projectionscreen according to the present invention.

[0064]FIG. 11 is a cross section of an element lens in a horizontaldirection contained in the micro-lens array sheet used in the projectionscreen according to the present invention.

[0065]FIG. 12 shows an example for a rear projection displaying deviceusing the micro-lens sheet according to the present invention.

[0066]FIG. 13 is a view showing structure of a screen in the projectiondisplaying device using the micro-lens sheet according to the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0067] Before explaining embodiments of the invention, here,light-condensing characteristics corresponding to a shape of the unitlens and chromatic difference of magnification are explained.

[0068]FIG. 1 is a cross section showing an optical path in a case inwhich a unit lens has a spherical shape (FIG. 3A) and a graph showingchromatic difference of magnification (FIG. 3B). FIG. 4A is a crosssection showing an optical path in a case in which a unit lens has anaspherical shape as defined as the present invention. FIG. 4B is a graphshowing chromatic difference of magnification.

[0069] According to FIG. 3, parallel lights which are incident to a unitlens 10 from a left-hand-side of the drawing are incident to a surfaceof a unit lens, and the parallel lights are refracted, then the parallellights are condensed so as to be focused in a right-hand-side of thedrawing. After that, the light is emitted so as to be spread in verticaldirection as shown in the drawing.

[0070] In this case, the focal length of the lights which are incidentin a central area of the unit lens is long (position of focus point isin a right-hand-side in the drawing), and the focal length of the lightswhich are incident in a marginal area of the unit lens is short(position of focus point is in a left-hand-side in the drawing) becauseof aberration due to a spherical lens. This is called an axial chromaticaberration.

[0071] On the other hand, because of aberration due to a spherical lens,a graph for showing a chromatic difference of magnification: FIG. 3A isobtained under condition that a center of the unit lens is plotted in ahorizontal axis such that y=o, and a distance between a position where athe emitted light and a light emitting surface cross is plotted as A yon a vertical axis (EY) such that when y=0, then A y=0.

[0072]FIGS. 4A and 4B show a case in which the unit lens has a shape inwhich there is less aberration due to spherical lens. As shown in FIG.4A, in this case, focus points approximately coincide over a central areto marginal area on the unit lens (there is a less axial chromaticaberration). Accordingly, FIG. 4B indicates that there is a littlefluctuation in EY; thus, there is less chromatic difference ofmagnification.

[0073]FIG. 6 is a curve showing an example for a cross sectional shapeof a unit lens according to the present invention in which there is lesschromatic difference of magnification.

[0074] Here, in the micro-lens sheet according to the present invention,its usage is not limited to a transmission projection screen. That is,the micro-lens sheet according to the present invention can be used fora light guiding member for controlling a lighting light from the lightsource in a uniform brightness and in a uniform emission direction in adisplay screen in a display having a built-in light source such as abacklight in a non-large size (30 inch size like in atransmission/reflection projection screen) transmission projectionscreen.

[0075] Operation

[0076] According to optical characteristics corresponding to shape of anunit lens, in case of rear projection secreen, it is preferable thatemission direction of the display light is controlled so as to be wideto an optical axis (normal direction to a screen main surface) in thatthe perspective scope can be widened without depending on lightdiffusing agent and a cost for a screen does not increase because a lotof light diffusing agent is not necessary.

[0077] In the present invention, light emission angle of each lens iswider than ±30 degrees to an optical axis; therefore, it is possible toobtain necessary perspective angle characteristics for a transmissionscreen. Furthermore, following operational effect is anticipated.Improvement in BM ratio

[0078] As explained above, BM pattern can be formed by using lightcondensing patter by self-alignment method in case in which parallellights are incident to fine lenses on a micro-lens sheet. In a fine unitlens having chromatic difference of magnification according to thepresent invention, it is possible to make an aperture area quite small.

[0079]FIG. 7 is a graph showing a distribution of exposure on a BMsurface in case in which a unit lens has an aspherical shape as definedin the present invention. Here, the shape of the light condensingsection is in a pulse wave form; thus, a borderline between the lightcondensing section and the non-light-condensing section is clear. Inorder to form BM by a self-alignment method, it is possible to recognizea shading layer forming section and a shading layer non-forming sectionaccording to whether or not there is an adhesive section of thephotosensitive adhesive easily. Therefore, it is possible to form ashading pattern clearly. By doing this, it is possible to obtain BMhaving high shading ratio (75% or higher); thus, it is possible toobtain a screen which can display high contrast image easily.

[0080] Under condition that a borderline between a surface on which BMis formed (in case of self-alignment method, a surface of photosensitivemember) and a base member for lens sheet is defined as a “focusingsurface”, by limiting the fluctuation range of the chromatic differenceof magnification in 50% of the diameter of a unit lens or lower, it ispreferable to form BM in 75% of BM area ratio (shading ratio) or higher.Furthermore, by limiting the fluctuation range of the chromaticdifference of magnification in 31% of the diameter of unit lens orlower, it is preferable to form BM in 90% of BM area ratio (shadingratio) or higher. Thus, it is possible to improve not only contrast butalso SIN greatly.

[0081] Improvement in Product Yield

[0082] When BM is formed by self-alignment method, more lights arecondensing because of smaller aberration due to spherical lens.Therefore, illumination in the exposed section increases; therefore, S/Nto an external light (non-parallel light emitted through the unit lens)improves. As a result, it is possible to obtain a lens sheet havingaccurate shading pattern which is quite independent to disturbance suchas the external lights.

[0083] Also, by disposing a lower refractive index layer than that ofthe lens sheet as a photosensitive member layer, and by adjusting thethickness of the lower refractive index layer, it is possible to adjustthe accuracy of BM easily.

[0084] Embodiments in the present invention are explained as followswith reference to drawings.

[0085] First Embodiment

[0086]FIG. 12 is a cross section showing a general structure of a liquidcrystal rear projection television. Reference numeral 31 is a lightsource lamp. Reference numeral 32 indicates an optical structuralsection. Reference numeral 33 indicates a liquid crystal panel.Reference numeral 34 indicates a first mirror. Reference numeral 35indicates a projecting lens. Reference numeral 36 indicates a secondmirror. Reference numeral 37 indicates a screen. FIG. 13 is a crosssection viewed in A-A section in the screen 37. In FIG. 13, Referencenumeral 38 indicates a Fresnel lens. Reference numeral 39 indicates amicro-lens. Reference numeral 40 indicates a black matrix section.Reference numeral 41 is a protection layer. Reference numeral 42indicates a hard-coat section.

[0087]FIGS. 1A and 1b are cross sections showing a micro-lens sheet 10.

[0088] On one surface of a base board 11, the micro-lens array section12 made from a reacted product of radioactive-ray-curable-resin isbonded. In the micro-lens array section 12, unit lenses 13 having anaspherical surface are disposed in 200 μm pitch or shorter (preferably100 μm or shorter).

[0089] In FIG. 1A, the neighboring unit lenses 13 are contacting eachother. As shown in FIG. 1B, it is acceptable that the neighboring unitlenses 13 are separated.

[0090] Unless there is a requirement for fine resolution such that theunit lenses 13 are disposed in 100 μm pitch or shorter, there is nonecessitiy that the micro-lens array section 12 is formed by a reactedproduct of a radioactive-ray-curable-resin; thus, it is acceptable thatthe micro-lens array section 12 is formed by performing press moldingoperation to a surface of the thermoplastic resin sheet.

[0091]FIGS. 2A to 2D are plan views showing a micro-lens sheet 10 shownin FIG. 1.

[0092] Unit lenses 13 are disposed in an approximate matrix form having200 μm pitch or shorter on a surface of the base board 11. There is nolimitation in the disposition. Matrix disposition such as a neat gridcondition, delta disposition as shown in FIGS. 2B and 2C, honeycombdisposition shown in 2D using hexagonal unit lens are acceptable.

[0093] In the drawings, it is defined that the neighboring unit lensarea indicates a case in which unit lenses contact by member (ofrectangle such as hexagon, etc.)

[0094] Here, the shape of the unit lens defined in the present inventionis rectangle as shown in FIGS. 2A and 2C. In case of FIG. 2B, the shapeof the unit lens defined in the present invention is a triangle. In caseof FIG. 2D, the shape of the unit lens defined in the present inventionis hexagon. In case of FIG. 2A, a lens section (curvature) which isindicated by a circle in the unit lens is provided. It is acceptablethat overall unit lens having shapes such as rectangle, triangle,hexagon constructs a lens section (curvature). Here, it is defined thatneighboring unit lenses indicate a case in which the unit lenses arecontacting by their member of rectangles in a case of FIGS. 2A to 2D.Also, it is defined that disposition pitch between the unit lensesindicates a distance between centers of the unit lenses.

[0095] In cases of FIG. 2a (square), FIG. 2B (regular triangle), FIG. 2D(regular hexagon), disposition pitch between the neighboring unit lensesis uniform. In case of FIG. 2C (rectangle), it is understood that thedisposition pitch of the unit lenses in an array n and the dispositionpitch of the unit lenses in an array n and an array n+1 are different.

[0096] Here, in case of disposition shown in FIG. 2A, as explained in acase of FIG. 1, it is anticipated that the neighboring unit lenses 13are contacting. Also, it is anticipated that the neighboring unit lenses13 are separating.

[0097] In cases of dispositions shown in FIGS. 2B, 2C, and 2D, there isa finer periodicity (periodicity of 100 μm made by a combination ofperiod a and period b in an example shown in FIG. 2C) than that of thedisposition pitch (tentatively, 100 μm) between the unit lenses 13.Thus, moiré which is caused by pitch ratio in the projected pixel fromthe projector can be further reduced; therefore, the present inventionis superior.

[0098] In order to produce such a micro-lens sheet 10, a molding stamperis manufactured, and after that, molding method such as press moldingmethod, extruding method, or photo-polymer method (hereinafter called 2Pmethod) is employed.

[0099] The above stamper has a counter-shape of the micro-lens sheet 10(that is, surface shape for corresponding to the unit lens section is inconcave shape). In order to manufacture such a stamper, a method forengraving a concave section on a surface of a metal layer by using amachine (or eroding chemically) or a method for engraving the concaveshape by using a laser can be used.

[0100] In any methods, it is not necessary to say that it is necessaryto form the shape of the curvature of the unit lens accurately;therefore, a suitable method is selected according to the purpose(fineness).

[0101] Also, a position of a valley part from a top of the lens(distance from a surface of a base member) is determined by curvatureshape of the unit lens. In case in which the unit lens is in a symmetricsquare shape or symmetric hexagonal shape, such as position differsaround the unit lens.

[0102] The shape of curvature of the unit lens may be spherical oraspherical. Also, it is necessary to control the shape of the concavesection severely such that the diffusing characteristics in a horizontaldirection and a vertical direction should be controlled so as to bedifferent each other.

[0103] Also, in order to form a shading layer on a flat surface of thebase board 11 which is disposed on the micro-lens sheet 10 so as to beaway from the lens section, a method in which a photosensitive layer (aknown member of which adhesion is lost by exposing a light) is formed onentire surface of the flat surface, and the photosensitive layer isexposed by the micro-lens array so as to change the characteristics ofthe photosensitive layer in an area corresponding to a light-condensingsection, and ink and a toner are attached to an area as anon-light-condensing section (know method called self-alignment by thelens it self) is preferable so as to form a shading layer in accuratepositions (not shown in the drawings).

[0104] Second Embodiment

[0105]FIG. 5 is a cross section showing an example for a micro-lenssheet 101 according to the present invention.

[0106] On one surface of a transparent supporting member 103, a lenssection (unit lens group) 102 is formed by using a reacted product ofradioactive-ray-curable-resin. A shading patter (BM) 105 having anaperture in a spot manner is formed in a position corresponding to anon-light-condinsing section by each of the unit lens on a flat surfacewhich is opposite to the transparent supporting member 103 via apositive photosensitive adhesive layer 104.

[0107] For a transparent supporting member 103, polyethyleneterephthalate (PET) or polycarbonate (PC) can be named.

[0108] It is preferable that the diameter of the unit lens and itsdisposition pitch are 200 μm or less so as to obtain a screen which issuitable for observing the fine resolution image.

[0109] Such a fine pitch operation can be obtained by performing amolding operation for forming a lens according to 2P method(photo-polymer method) by using the hardened product of theradioactive-ray-curable-resin.

[0110] In an example shown in FIG. 5, a lens section having asphericalshape with 80 μm diameter is formed on one surface of the transparentsupporting member 3 having 1.50 refractive index and 75 μm thicknessaccording to 2P method by using the hardened product of theradioactive-ray-curable-resin.

[0111] In a case of example shown in the above drawings, the maximumwidth of the chromatic difference of magnification is 6 μm (7.5% to thediameter of lens); thus, it is possible to form BM with 92.5% of shadingratio.

[0112] Even if the same material is used in the same dimension, in casein which the shape of the unit lens is spherical, the maximum width ofchromatic difference of magnification is 30 μm (37.5% to the diameter ofthe lens); thus, the maximum available shading ratio of BM is 62.5%.

[0113] By using by one piece of the above micro-lens sheet or aplurality of micro-lens sheet in a connected manner in a rear projectiondisplaying device having 30 inch size or larger, it is possible to watchhigh contrast image with wider perspective angle.

[0114] In case of a micro-lens sheet, comparing to a case of lenticularsheet having cylindrical lens group, the connected part of the lenssheets do not look seamy; thus, there is less disadvantage for alarge-size display.

[0115] Also, in the above case, a Fresnel lens sheet is disposed to aprojector as an image light source, it is possible to shorten thedistance between the projector and the screen when parallel lights areincident to the micro-lens sheet. By doing this, it is possible not onlyto reduce the size of the displaying device but also emit the displayingimage light having high brightness only to a necessary range; thus, itis preferable.

[0116] Also, in the above case, it is acceptable that a light diffusinglayer in which a light diffusing agent is dispersed is disposed in theFresnel lens and/or the micro-lens sheet.

[0117] For a light diffusing agent to be used here, a particle made frominorganic member such as silicon, aluminum, calcium, inorganic powderand glass beads containing oxide of these member, organic member such asacrylic resin, styrene resin, polycarbonate resin, acrylic/styrenecopolymer resin can be named.

[0118] In order to select the light diffusing agent, it is necessary totake following factors into account such as optical characteristics suchas refractive index difference to a binder resin, illumination on itssurface, dispersion for forming a light diffusing base member or lightdiffusing ink, and fragility during a molding operation. For an averagediameter of the particle, 5 μm or larger is preferable. More preferably,5 to 20 μm, further more preferably, 5 to 10 μm is preferable.

[0119] By compatibly use the light diffusing layer, it is possible tocontrol the perspective angle by alleviating the steepness of thebrightness reduction even in distant observing direction. Also, there isan improvement in focusing function by using gaps (mat surface) in afine lens array. In addition, there is an improvement in focusingfunction for image light.

[0120] The finer the unit lens is, the more similarly the surface of thelens section of the micro-lens sheet works. Therefore, there is lessdependency to the light diffusing layer using the light diffusing agent.In contrast, in a case in which there is not sufficient focusingcharacteristics and light diffusing characteristics only by the surfaceof the lens, the light diffusing layer is compatibly used.

[0121] Also, for a projection screen, the above micro-lens sheet can beused not only to a rear projection displaying device but also to a frontprojection displaying device having 30 inch size or larger if themicro-lens sheet.

[0122] When the above micro-lens sheet is used for a reflection screen,a light diffusing layer is formed on an entire surface of the micro-lenssheet away from the lens section.

[0123] Furthermore, it is possible that the above micro-lens sheet isused for a light guiding member for controlling the lighting light fromthe light source such that the lighting light is emitted so as be in auniform brightness in a uniform emitting direction in a display screen.

[0124] For such a representative displaying device, a liquid crystaldisplaying device (monitor or mobile terminals, etc.) having a backlightcan be named.

[0125] Third Embodiment

[0126] Embodiments of a projection screen as an example for the presentinvention is explained as follows with reference to the drawings.

[0127]FIGS. 8A and 8B are general views for an element lens of amicro-lens sheet used in a projection screen according to the presentinvention.

[0128]FIG. 9 is a perspective view of an element lens contained in themicro-lens array sheet used in the projection screen according to thepresent invention.

[0129]FIG. 10 is a cross section of an element lens in a verticaldirection contained in the micro-lens array sheet used in the projectionscreen according to the present invention.

[0130]FIG. 11 is a cross section of an element lens in a horizontaldirection contained in the micro-lens array sheet used in the projectionscreen according to the present invention.

[0131] Here, regarding the lens array sheet shown in this embodiment,the shape of the lens are actually designed, and these drawings are madeaccording to these designed lens shape.

[0132] In FIG. 8B, thickness (distance from a flat surface which is awayfrom the lens surface to a top of the lens) of an entire lens sheet isuniform. In case of a unit lens having symmetric toric shape, thedistance from the top of the lens to a valley part is different indistance D1 in A-A′ cross section and distance D2 in B-B′ even in thesame unit lens.

[0133] Main feature of the lens array sheet is in a shape of the elementlens contained in the lens array layer. The lens array layer comprises abase member layer in a board manner and a lens layer which is disposednear there.

[0134] The element lens contained in the lens array is in an asphericalshape. The element lens also is asymmetrical to an axis of the lenshaving geometrically three-dimensional shape. In its cross section,aspherical shapes such as not only aspherical shape, but also ovalshape, parabolic shape, and an aspherical shape including higher termsare included.

[0135] By using such a lens having aspherical and asymmetrical shape,the incident light (3) which is incident in parallel direction to theelement lens are refracted according to the incident position on aincident surface (1) due to difference of refraction angle at the timeof light emission. As a result, it is possible to differentiate therefractive index of the light to an orthogonal axis of coordinates on asurface which is orthogonal to the optical axis (equivalent to ahorizontal axis and a vertical axis in a screen which is disposedperpendicularly); therefore, it is possible to obtain a lightdistributing characteristics according to the purpose (see FIGS. 10 and11).

[0136] More specifically, as shown in FIGS. 10 and 11, there is aphenomena that the light condensing position of the emitted light (4) isdifferent in a thickness direction. The light emission angle of thelight at that time is equivalent to the light distributing anglecharacteristics.

[0137] For a lens array layer, plastic member which is as transparent asplastic member and glass member is preferable. Furthermore, a plasticmember which can be limitlessly used for an optical member is morepreferable from a production efficiency point of view.

[0138] For such a plastic member, acrylic resin such aspolymethyl_methacrylate, polycarbonate resin, acrylic-styrene copolymer,styrene resin, polyvinyl chloride resin can be named.

[0139] Also, for a member for a lens layer, aradioactive-ray-curable-resin such as an ultraviolet-ray-curable-resinor an electronic-ray-curable-resin should preferably be used because itis possible to perform a fine-pitch-forming operation. For such aradioactive-ray-curable-resin, for example, components containingurethane (meth) acrylate, and/or epoxy (meth) acrylate oligomer to whicha reacted diluted agent, photopolymerization starting agent, opticalsensitizer are doped can be used. An urethane (meth) oligomer, althoughthere is no particular limitation, can be obtained reacting, by forexample, polyols such as ethylene glycol, 1, 4-butanediol, neopentylglycol, polycaprolactone polyol, polyester polyol, polycarbonate diol,polytetramethylene glycol, and polyisocyanates such as hexamethylenediisocyanate, isophorone diisocyanate, tolylene diisocyanate, xyleneisocyanate. Epoxy (meth) acrylate oligomer can be obtained by reactingepoxy resins such as bisphenol-A type epoxy resin, bisphenol-F typeepoxy resin, phenol novolak type epoxy resin, terminal glycidyl ether ofbisphenol-A type propylene oxide adduct, and fluorine epoxy resin and(meth) acrylic acid.

[0140] A lens array layer can be produced, for example, as follows. Aradioactive-ray-curable-resin is applied on a base member layer made ofa plastic member under condition that the radioactive-ray-curable-resinis not hardened. From above there, a molding stamper is pushed, and apredetermined radioactive ray is emitted so as to harden it. Thus, alens layer is formed.

[0141] A molding stamper can form a lens layer, for example, in afollowing manner. By using a photo-lithography method, at first, aplurality of mask on which a cross sectional shape for the element lensis patterned are prepared. By using the masks, silicon wafers areexposed consequently. After that, by performing an etching operationsuch as RIE. Patterning operations are repeated in its depth direction;thus, a molding stamper having a designed shape can be obtained.

[0142] As explained above, a lens array sheet layer can be produced bythe same method as used for producing a conventional lenticular lens.

[0143] A photosensitive resin layer and a shading layer can be producedas follows. Fresnel lenses are disposed in parallel under the samecondition as the practical use for a projection screen. Alight isemitted from the lens layer of the lens array sheet via the Fresnellenses. The characteristics in the photosensitive resin layer in a partwhich is exposed by the light which passes through the lens array layerchanges, and adhesive characteristics is lost. The, a transfer filmhaving a black transfer layer containing a black carbon is pushed to thephotosensitive resin layer. Accordingly, the transfer layer istransferred to an unexposed region having adhesive characteristicsselectively. Thus, the shading layer is formed.

[0144] The shading layer is formed corresponding to the focusing patternin a line-segment state due to the light condensation because of thetoric micro-lens. The position of such focusing pattern represents anastigmatism due to the toric micro-lens approximately. Therefore, thefocusing pattern appears in two points in an optical axis direction(thickness direction). Among these focus points (called, in a field ofgeometric optics, a sagital focus point and a meridional focus point),the most preferable position for forming the lens sheet is adjusted byperforming a sandwiching adjustment for low refractive index layer(otherwise, the lens is designed a such). By disposing a black shadinglayer in this position, it is possible to obtain a high rate BM pattern.Here, a lower refractive index layer is used. This is because of itsweak refractive force; thus it is possible to anticipate largertolerance for thickness; therefore, it is possible to improve itsformability.

[0145] Consequently, on this shading layer, by disposing an adhesiveagent layer, light diffusing layer, and a hardcoat layer according tonecessity, it is possible to obtain a lens array sheet.

[0146] As explained above, in this lens array sheet, by preferablydesigning a shape of one toric lens array, it is possible to control thelight distributing characteristics (perspective angle) of a light whichtransmits through the lens array sheet in both a horizontal directionand a vertical direction. In particular, by making its ratio at 2/3 orlower, it is possible to distribute the vertical/horizontal lightdistributing characteristics for a preferable projection screen. Thus,it is possible to obtain preferable characteristics for a screen.

[0147] Furthermore, it is possible to reduce cost for members used inthe production and manufacturing process compared to a case in which twolens layers are used or the lens layers are formed on both surfaces ofthe base member layer.

[0148] Also, by simplifying the light diffusing layer, it is possible toreduce the absorption of the light or decrease of gain in the lightdiffusing layer. As a result, it is possible to control white-scatteringphenomena which is caused by the light diffusing layer; thus, it ispossible to realize high S/N ratio.

[0149] Furthermore, by adding the Fresnel lens, it is possible toshorten the emission distance from the projector. By establishing suchcompatibility, it is possible to obtain a superior screen.

[0150] Here, there is no particular limitation in factors such asthickness of each layer of the lens array sheet according to the presentinvention, and pitch of the lens array. These factors can be changedpreferably.

EXPERIMENTAL EXAMPLE

[0151] The present invention is explained with reference to experimentalexample more spedifically as follows.

[0152] In this experimental example, designing parameter is determinedas follows. Effect in the present invention is examined.

[0153] Designing Parameter

[0154] In a base member layer of the lens array layer is made frompolyethylene terephthalate with 0.075 mm thickness. Lens layer in thelens array layer is made such that the material is UV photosensitiveresin, pitch between the lenses is 0.080 mm, the shape of cross sectionin which the lens thug (height of convex section of the lens) is large(corresponding to a horizontal direction in the screen) is oval, thecross section in which the lens thug is small is spherical, ratio ofthug amount is 2:1 so as to form a toric shape. For a photosensitiveresin layer, a Cromalin film (Trademark, registered by DUPONT) having 20μm thickness is used.

[0155] To a surface of the lens on this lens array sheet, parallel lightwhich is collimated in 1 to 5 degrees is emitted so as to perform apatterning operation for the photosensitive layer. Then, a black filmhaving 2 μm thickness (transfer film of carbon black) is transferred soas to be a shading layer; thus, it is possible to obtain a shading layerhaving an aperture corresponding to a micro-lens contained in the lensarray.

[0156] The lens array surface of the lens array sheet which is obtainedin this way is disposed toward the light source. By using the lens arraysheet for diffusing the light, it is possible to observe that theperspective angle corresponding to a shape of the lens array can beobtained respectively.

INDUSTRIAL APPLICABILITY

[0157] The micro-lens sheet according to the present invention issuitable for producing a rear projection screen having simple structurein which two lens sheets are assembled in combination with a Fresnellens. It is preferable to watch high resolution quality image withoutmoire.

[0158] According to the micro-lens sheet in the present invention, it ispossible to control the light emission direction (range) of the displaylight from the lens section so as to be wide in a perspective range bydisposing the unit lens group in fine pitch such as 200 μm or shorter.

[0159] In particular, according to the present invention, it is easy toform a black matrix with fine pitch such that the borderline between theaperture section and the shading section is clear so as to form a blackmatrix having high shading rate (75% or higher) on the micro-lens sheetaway from the lens section.

[0160] Furthermore, according to the micro-lens sheet having amicro-lens array section which is used for the projection screenaccording to the present invention, it is possible to control the lightdistributing characteristics of the transmitting light through the lensarray layer in a vertical direction and a horizontal direction bypreferably changing the shape of toric shape of the element lens. Thisfact indicates that it is possible to control the opticalcharacteristics of the screen positively; thus, there is a great effectin reducing the time and cost necessary for product development.

[0161] Also, it is possible to set the perspective angle independentlyin a vertical direction and a horizontal direction on one piece ofmicro-lens sheet desirably. Therefore, (1) it is possible to reduce thecost necessary for production and (2) it is not necessary to develop andprepare the necessary material because the amount of the light diffusingagent can be set according to the available material. Also, (3) it ispossible to restrict the absorption of the light (light loss).Therefore, there is an effect in that it is possible to obtain a brightprojection screen using the micro-lens sheet easily.

[0162] Also, it is possible to reduce the amount of the light diffusingagent comparing a case of the conventional screen. Therefore, reflectionand scattering of the external light are restricted; thus, transparencyincreases. Therefore, light absorbing function in enhanced. Thus, it ispossible to obtain a projection screen using the micro-lens sheet havingconventionally unrealized improved S/N.

1. A micro-lens sheet having a micro-lens array section in which unitlenses are disposed in approximate matrix in a second dimensional manneron at least one surface of a base board wherein the micro-lens arraysection is formed on only one surface of the base board; the micro-lensarray section includes the unit lens having an aspherical shape; anddisposition pitch of neighboring unit lenses is 200 μm or shorter.
 2. Amicro-lens sheet having a micro-lens array section in which unit lensesare disposed in approximate matrix in a second dimensional manner on atleast one surface of a base board wherein the micro-lens array sectionis formed such that a reacted product of a radioactive-ray-curable-resinis bonded on only one surface of the base board; the micro-lens arraysection includes the unit lens having an aspherical shape; anddisposition pitch of neighboring unit lenses is 100 μm or shorter.
 3. Amicro-lens sheet according to claim 1 wherein the micro-lens arraysection has only the unit lens having aspherical shape.
 4. A micro-lenssheet according to claim 1 wherein optical diffusion by each unit lensin the micro-lens sheet differs between a horizontal direction and avertical direction.
 5. A micro-lens sheet according to claim 1 whereinthe unit lens is disposed in rectangular grid.
 6. A micro-lens sheetaccording to claim 1 wherein the unit lens is disposed in deltadisposition or honeycomb disposition.
 7. A micro-lens sheet according toclaim 1 wherein a shading layer is formed in a non-light-condensingsection on which light is not condensed by the unit lens on an oppositesurface of the base board to the micro-lens array section
 8. Arear-projection screen wherein the lens array section of the micro-lenssheet according to claim 1 and a lens array section of a Fresnel lenssheet face each other such that the Fresnel lens sheet is disposednearer to the projector as a light source.
 9. A display device wherein alight source is a liquid crystal projector or a digital micro-mirrordevice; and the display device has the rear projection screen accordingto claim
 8. 10. A micro-lens sheet having a micro-lens array section inwhich unit lenses are disposed in approximate matrix in a seconddimensional manner on at least one surface of a base board whereindiameter for each of the unit lens and the disposition pitch is 200 μmor shorter; light emission angle which is emitted from each unit lens ismore than ±30 degrees against a normal of a main surface of themicro-lens sheet; chromatic difference of magnification which is causedby each unit lens is designed to be in a range of 0%<chromaticdifference of magnification≦50% of the diameter of the lens.
 11. Amicro-lens sheet according to claim 10 wherein a shading layer is formedon another surface of the base board which is disposed away from themicro-lens array section such that a light-condensing section by eachunit lens become an aperture section.
 12. A micro-lens sheet accordingto claim 11 wherein the shading layer if formed so as to have an areawhich is 75% of an entire area of the micro-lens array section orlarger.
 13. A micro-lens sheet according to claim 11 wherein the shadinglayer is formed on a surface of the non-light-condensing section on aphoto-sensitive resin layer in which the light-condensing section andthe non-light-condensing section are formed according to thelight-condensation of the micro-lens array section.
 14. A micro-lenssheet according to claim 13 wherein the photo-sensitive resin layer isformed on a surface of the base board which is away from the micro-lensarray section via a transparent resin layer having lower refractiveindex than that of the base board or the photo-sensitive resin layer isdirectly formed on a surface of the base board so as to have lowerrefractive index than that of the base board such that thephoto-sensitive resin layer is disposed away from the micro-lens arraysection.
 15. A rear-projection screen which size is 30 inches or largerusing the micro-lens sheet according to claim
 9. 16. A projection screenaccording to claim 15 wherein the Fresnel-lens sheet is disposed on theprojector as a projection light source.
 17. A projection screenaccording to claim 15 wherein the light-diffusion layer in which a lightdiffusion member is dispersed is disposed near either one of theFresnel-lens sheet or the micro-lens sheet.
 18. A front-projectionscreen which size is 30 inches or larger having the micro-lens sheetaccording to claim 10 and the light-reflection layer which is disposedon a surface of the base board which is opposite to the lens.
 19. Adisplay device having a backlight having the micro-lens sheet accordingto claim 10 as a light-guiding member for controlling a light emissionfrom the light source under condition of uniform brightness or in auniform emission direction in a display screen.
 20. A projection screenhaving the micro-lens sheet having the micro-lens array section in whichthe unit lenses are disposed in an approximate matrix in asecond-dimensional manner wherein a surface of the unit lens is formedin toric shape as a continuous surface such that curvature of crosssectional shape of the unit lens in one direction is smaller than thatin an orthogonal direction to the particular direction; the micro-lensarray section in which the unit lens is disposed in an approximatematrix in a second-dimension manner is formed on one surface of thetransparent sheet; and the shading layer having the aperture section ofwhich optical axis is aligned with the optical axis of unit lens groupon a surface of the sheet which is disposed opposite to the micro-lensarray section.
 21. A projection screen according to claim 20 whereindirections of the curvature of each unit lens are uniformly disposedwhen the micro-lens array section in which the unit lens is disposed inan approximate matrix in a second-dimension manner is formed on onesurface of the transparent sheet.
 22. A projection screen according toclaim 20 wherein lens thug of the toric surface which is a ratio betweenthickness of a curvature section in a one direction and thickness of acurvature section in a cross sectional surface in an orthogonaldirection is 2/3 or smaller.
 23. A projection screen according to claim20 wherein lens thug of the toric surface which is a ratio betweenthickness of a curvature section in a horizontal direction and thicknessof a curvature section in a cross sectional surface in a verticaldirection is 2/3 or smaller.
 24. A projection screen according to claim20 wherein the micro-lens array section is formed on one surface of thetransparent sheet which is disposed in an area from which a light isincident (near a projector) when the micro-lens array section is usedfor a transparent projection screen.
 25. A projection screen accordingto claim 20 wherein the shading layer is formed in thenon-light-condensing area on a surface of a base board opposite to thelens such that a light does not condense by exposing a light through themicro-lens array section; the photosensitive resin layer or a layerwhich is formed on a surface of the photosensitive resin layer is a baseboard for a lens such that the refractive index of the layer is lowerthan that of the transparent sheet.
 26. A projection screen furtherhaving a Fresnel lens having a concentric ring band near a lightincident region (near a projector) when the projection screen accordingto claim 20 is used for a transparent projection screen.
 27. Aprojection screen according to claim 26 wherein a shape of a unit lensarea is triangular, hexagonal, or rectangular.